Various manually operated devices have been suggested for holding of the opposite ends of an elongated chain unit during link replacement, servicing and the like. Multiple part vice-like members have been suggested, for example, as shown in U.S. Pat. No. 3,901,476, wherein a pair of elongated jaw members are pivotally interconnected to a common support. An appropriate expansion mechanism includes a rotating threaded shaft member mounted through similar followers for pivoting the jaw members and thereby expanding and retracting one member relative to the other. A somewhat similar device is also shown in U.S. Pat. No. 3,999,738. In addition to such pivotally mounted devices various threaded members provided with interconnecting jaw members have been suggested. For example U.S. Pat. No. 1,373,230 to S. H. Gainor discloses a drive-chain clamp arrangement wherein an L-shaped bolt is journaled in a support having an opposing jaw whereby the movement of a nut on the bolt causes retraction to close the jaw members for drawing of a chain together. A similar chain clamp with a somewhat more complex jaw mounting arrangement is shown in U.S. Pat. No. 752,074. A further threaded bolt-type unit wherein both of the jaw members are carried to the opposite sides of a rotating threaded shaft is shown in U.S. Pat. No. 762,060. A similar L-shaped chain tightener is also shown in U.S. Pat. No. 775,355 which issued Nov. 2, 1904. Although such devices may well provide a means for holding of the opposite ends of a chain for servicing or the like, they have various disadvantages as far as requiring special constructed parts, pivot connections and the like all of which provide a relatively expensive and complex construction. The Gainor patent would appear to provide a somewhat simpler and less complex and less expensive structure. However, its approach and concept would appear to have certain disadvantages, particularly from the standpoint of life and efficiency of operation. For example, moving of a threaded member through the journal portion of the support with the end extending substantially therefrom would tend to create interference between the bolt member and the support. This could create a drag and/or wear on the threads and/or the base support within which the bolt is moving. With the threaded construction, such interference could result in a very rapid wear of the threads or base member as well as contribute to an inefficient mechanical movement. Further, with the structure as illustrated, a relatively special tubing and housing construction is required, with a relatively heavy base support member having a first bore within which the support rod is located and a second enlarged bore within which the L-shaped end of the rod member can move. Although this should not effect the operability or efficiency of the device, it may well contribute to the cost of the device.
Thus, although there has been many suggestions and variations in chain coupling devices, they have certain distinct disadvantages from the standpoint of either cost, complexity, operation and the like.
Further, many of the prior art devices are not conveniently used in chain applications which have very limited space within which to operate. Thus in many applications, the chain will be confined within a housing-typed structure and access for servicing the chain and the like may be extremely restricted. In such cases many of the prior art devices would of course be completely inoperable because of the limited areas within which to operate. Although, some such as the Gainor patent, could perhaps be in such a location, they have certain other disadvantages.
Thus, although various prior art device have been suggested, all such devices are believed to suffer from certain practical considerations such as cost, complexity, life, use and the like.